The disclosure is based on an adjustment device according to the description below and on a hydraulic machine having such an adjustment device.
DE 199 49 169 C2 discloses such an adjustment device for adjusting a pivoting cradle of an axial piston machine. A pivoting angle of the pivoting cradle can be pivoted here by means of an actuating piston which acts on the pivoting cradle. In order to reduce the pivoting angle, pressure medium is fed to an actuating pressure space adjoining the actuating piston. In the direction of increasing the pivoting angle, a restoring spring (not shown in the document) acts on the pivoting cradle. In order to increase the pivoting angle, pressure medium is discharged from the actuating pressure space, with the result that the restoring spring can pivot back the pivoting cradle and shift the actuating piston. The actuating pressure which is present in the actuating pressure space is set in accordance with the force necessary to adjust and to hold the pivoting cradle. The inflow of pressure medium into the actuating pressure space and the outflow of pressure medium out of the actuating pressure space are controlled by a control valve. This is arranged coaxially with the actuating piston in a common recess together with the actuating piston. A control piston of the control valve can be shifted here in a first direction out of a control position in the direction of the actuating piston by means of a lifting magnet. During such shifting, a pressure medium connection between the actuating pressure space and a low pressure area of the axial piston machine is opened. In the opposing, second direction, that is to say in a direction away from the actuating piston, a spring force is applied to the control piston via a return spring which is supported on the actuating piston, which spring force converts the position of the actuating piston and therefore of the pivoting cradle into a force acting on the control piston, that is to say returns the position of the pivoting cradle as a force signal to the control piston. When the control piston shifts from the control position in the second direction, the control piston opens a pressure medium connection between the actuating pressure space and a high pressure side of the axial piston machine. In order to apply the spring force, the control piston projects out of the valve housing with its end section into the actuating pressure space, wherein a spring plate for the return spring is arranged on the end section. Through the return spring, the control piston has a mechanical operative connection to the actuating piston, which brings about a situation in which, by controlling the pressure medium connection between the actuating pressure space and the low pressure side or the high pressure side of the axial piston machine, the control piston sets a specific pivoting angle of the pivoting cradle as a function of a control force which is applied electromagnetically or hydraulically or in some other way to it counter to the force of the return spring.
In data sheet RD 92703/08.11 by the applicant, a further embodiment of an axial piston machine with a pivoting cradle is illustrated. In this context, a return spring is provided which is also supported on the actuating piston and which applies a spring force to the control piston via a spring plate. The spring plate is in turn supported on an end side of the control piston. An axial drilled hole of the control piston opens into the end side, which axial drilled hole is connected to a control connection of a further control valve pressure controller or pressure delivery current controller connection of the control valve and functions together with the return spring and the spring plate as a nonreturn valve if the other control valve outputs a signal to pivot the pivoting cradle, that is to say to reduce the pivoting angle.
A disadvantage with the embodiments explained above is that they are of complex configuration in terms of device technology.
In contrast, the disclosure is based on the object of providing an adjustment device and a hydraulic machine having such an adjustment device which are constructed in a simple way in terms of device technology.